Then perhaps we should be more honest about what the concern is and the requirements of our jobs. Employers are paying for you to be on call for 8 hours a day (minimum) not just for your output. You need to be responsive and attentive as part of your job, not complying immediately can result in demerits.
I have a friend who was quick to respond to Slack messages as he napped close to his phone most of the time while WFH, but in between the responses he did very little work.
100% true story.
You make an interesting point. I think in the office, what you wrote is the unwritten rule and people understand it automatically. At home it needs to be explicitly written down and it appears the employer is particularly abusive if they say you are expected to sit down at your VC and leave video on. Just demanding RTO is much easier and better PR for the HR.
I'm not surprised, part of the lessons of this great experiment imo is a lot of jobs aren't actually important and are just part of empire building efforts and HEADCOUNT. Real actual work gets done by a few people, and a lot of these organizations have absolutely no idea who those people are, in office or not.
Agreed on your last paragraph, no one wants to say that, and just making everyone RTO seems to be the less offensive way to accomplish the goal: control of an employee's time. The alternative that they will go with next is probably employee spyware, in fact I imagine it's already in use at many companies.